Ford’s all-new, sixth-generation Mustang is now just a couple of months away from hitting the showroom floor, in base, EcoBoost and GT trim. Here we have the latter, which revs its 5.0-liter V-8 engine for all the world to enjoy. DON’T MISS: 2015 Dodge Charger SRT Hellcat Is World’s Most Powerful Sedan Loping along at idle like it has a…